[Written by a veterinarian] Can cats get bitten by mosquitoes? The dangers of heartworm and safe insect repellent measures

Do you know about the disease called "heartworm disease"? If you own a dog, you may know it is a parasitic disease transmitted by mosquitoes, but for cat owners, it may be a less familiar condition. It is known that heartworms, which are vectored by mosquitoes, can parasitize not only dogs but also cats. In this article, we will explain heartworm disease in cats.

Can cats get bitten by mosquitoes? Areas prone to bites and symptoms to look for

Be careful with "ears, nose, and paw pads" where hair is thin

Mosquitoes appear more in the cool mornings and evenings than during the hot hours of the day. They can even enter your home through gaps in screen doors, meaning cats can get bitten while indoors. Mosquitoes are attracted to carbon dioxide, body heat, and body odor emitted by animals. Even for cats covered in fur, there is a risk of mosquito bites around the ears, on the nose, and on the paw pads, where the coat is thin.

Symptoms when bitten by a mosquito and first aid

Like humans, cats will experience redness and intense itching. Symptoms such as frequently scratching the bitten area with their paws or shaking their head may occur. The bitten area may also become red and swollen.

If your cat is itchy, do not easily use anti-itch medicine intended for humans. Human anti-itch products may contain ingredients that are harmful to cats. If the symptoms are severe, cool the area with water and visit a veterinary clinic.

[Veterinarian Warning] The terrifying "feline heartworm disease" transmitted by mosquitoes

What is feline heartworm disease (dirofilariasis)?

Heartworm (Dirofilaria immitis) is a parasite transmitted by mosquitoes. It parasitizes the heart and pulmonary blood vessels in dogs, but it can also infect humans and cats. When a mosquito carrying heartworm larvae bites, it enters the animal's body. At the time of entry, they are larvae about 1mm in size, but they grow to about 10–15 cm long and reside in the heart and pulmonary blood vessels. Since dogs are the natural host for heartworms, many larvae grow into adults, and females produce offspring (microfilariae) within the heart, which then circulate through the body via the bloodstream. While dozens to hundreds of adult heartworms can parasitize a dog's heart, cats are not the primary host, so most of them die; only about 1 to 3 reach the heart.

Hard-to-notice initial symptoms and the risk of "sudden death"

When a cat is infected with heartworms, they are often asymptomatic or show temporary symptoms like coughing. Because there are so few heartworms in a feline infection, it is difficult to detect them with test kits, making heartworm disease in cats harder to diagnose than in dogs. It begins with coughing, vomiting, dyspnea (asthma-like symptoms), or loss of appetite. If it becomes severe, it causes ascites, pleural effusion, and respiratory distress. It is a terrifying disease that, while very rare, can cause sudden death.

Why there is a risk of infection even with "strictly indoor" cats

Mosquitoes can enter the house through gaps in screen doors. Thinking "my cat doesn't go outside, so it's okay" is a big mistake. Data shows that even among indoor cats, there is an infection rate of approximately 10% for those that are not on heartworm prevention.

Are human insect repellents a no-go for cats? Dangers and precautions regarding essential oils and mosquito coils

Can standard mosquito coils and one-push sprays be used?

"Pyrethroid" insecticidal ingredients contained in standard mosquito coils and sprays can be used safely because they are broken down quickly in the bodies of mammals, including cats. However, if the agent is sprayed directly on them or used in a closed room, symptoms like vomiting, diarrhea, and drooling may occur, so you must be careful with ventilation and usage methods.

[Strictly Prohibited] Why aroma (essential oils) and herbal repellents are dangerous to cats

Essential oils such as peppermint oil and tea tree oil, which are commonly used in organic insect repellent sprays for humans, are highly toxic to cats. A cat's liver lacks the metabolic function known as "glucuronidation" required to break down fat-soluble components, meaning they cannot excrete these toxic substances, which leads to severe poisoning. Therefore, you should avoid using aroma oils and herbs.

[Safety Measures] Protect your beloved cat from mosquitoes! Prevention methods needed even for indoor cats

Reliable prevention through "heartworm preventatives" from a veterinary clinic

Since it is impossible to 100% prevent being bitten by a mosquito, monthly preventative medication (spot-on types, oral medications, etc.) is the most important and safest measure. Heartworm preventatives work by eliminating larvae that have entered the body. I am often asked in the exam room, "Is this medicine to prevent mosquito bites?" but it does not repel the mosquitoes themselves. You can prevent infection by using it regularly every month during the mosquito season (May to November). However, since the effect of the medicine lasts only about a month, the preventive effect will drop if it is not administered regularly.

Physical mosquito entry countermeasures you can take at home

While you cannot completely prevent the entry of mosquitoes, you can reduce it through countermeasures. Repair tears in screen doors, be quick when entering and exiting through the door, and eliminate sources of mosquito breeding (such as planter saucers that collect water) to curb their population.

Summary: To protect your cat from the threat of mosquitoes, ensure proper knowledge and thorough use of preventatives

Feline heartworm disease is not a well-known condition, but it is believed that it may increase in the future due to global warming. Even a small number of heartworms can lead to sudden death in cats. Since it can be prevented by regular deworming with heartworm medication, please ensure you maintain a regular administration schedule.

Trying to repel mosquitoes with aroma or herbs can be harmful to your cat. First, prioritize creating an environment that eliminates mosquito entry routes, and survive the summer by making an environment where both humans and cats aren't bothered by mosquitoes.

Related Articles

Veterinarian explains in detail which flea and tick preventative is best for cats

You received a DM from the vet about flea and tick prevention, but do you really need to prevent them if your cat is strictly indoors? The answer is yes. Fleas and ticks can hitch a ride on owners and enter the home. Fleas and ticks not only cause itching but also transmit various infectious diseases. In this article, we explain flea and tick preventatives for cats in detail.